1. Field of the Invention
The present invention relates to a photographing apparatus which mounts optical equipment, e.g., a camera or telephoto observation equipment, on its universal head, detects the distance between the setting point of the equipment and a target point, and can automatically control a focusing mechanism of the equipment.
2. Related Background Art
Conventionally, a known universal head apparatus for a television camera has no arrangement for automatically operating optical equipment, e.g., a camera, mounted thereon. Therefore, when the optical equipment, e.g., a camera, is mounted on the known universal head apparatus to perform a photographing operation, an operator of the universal head apparatus or an operator of a camera operates a focusing mechanism of the optical equipment manually or through a remote control unit. However, when an object which moves fast, e.g., in a sport, is to be photographed, this requires skill. Therefore, as sport programs are becoming popular, strong demand has arisen for an automatic focusing mechanism. For example, U.S. Pat. No. 3,538,830 describes a technique for obtaining the distance to an object through triangulation on the basis of the setting height of the camera and its tilt angle. According to this patent, when the distance to the object is measured, the object must be present on a ground plane perpendicular to the direction of gravity, the height of the camera from the ground plate must be substantially constant, and a tilt angle with reference to a plumb line when the camera is inclined must be known.
However, in the conventional method, a gravity pendulum for determining the plumb line is necessary. More specifically, the tilt angle of the universal head apparatus does not always correspond to the tilt angle of the camera with respect to the ground plane, but is an angle with respect to a predetermined plane when the universal head apparatus is arbitrarily set. In a method wherein the displacement of the focusing mechanism of, e.g., a camera is determined in accordance with the tilt angle, the setting position, particularly, the height, of the universal head apparatus must be accurately measured, and the universal head must be arranged to be completely parallel to the ground plane. Therefore, adjustment for accurately setting the apparatus takes a long period of time. Otherwise, accurate focusing displacement cannot be obtained.
Even if the height is accurately obtained with respect to the ground plane to allow the parallel adjustment and the predetermined relationship between the tilt angle of the universal head apparatus and the titt angle of the camera with respect to the horizontal plane can be obtained, when the relationship between a plane formed by the object to be photographed and the camera setting position does not satisfy a regular triangular relationship, it is impossible to obtain the distance to the object.
FIG. 1 illustrates a case wherein the universal head apparatus is arranged at a point H to be perfectly parallel to the ground plane perpendicular to the direction of gravity, e.g., parallel to a ground plane P0P2.
When a plane P0P1 formed by the object forms a predetermined angle .alpha. with the plane P0P2, and when triangulation utilizing the regular triangle is adopted, the distance measuring apparatus of the camera arranged at the point H determines, as the distance to the object, a line HA', i.e., l1, obtianed from a tilt angle .theta. formed by a height OH and a reference plane P3P4, thus performing focusing. However, in practice, since the distance from the camera to the object corresponds to a line HA, i.e., l0, the resultant image is often blurred.
In this distance measuring method, when the distance to the object is measured, light reflected from the object is received, and the distance to the object is calculated in accordance with the received light, thereby driving a focusing mechanism. However, in such a distance measuring apparatus, it is difficult to perform focusing with respect to an object having poor contrast or an object having a low light reflection property. In addition, since the light reflected from the object is received, this results in a complex optical system therefor.